#define _CRT_SECURE_NO_WARNINGS
#include"stack.h"
void STInit(ST* ps)
{
	assert(ps);
	ps->capacity = 0;
	ps->top = 0;
	ps->a = NULL;
}

void STDestroy(ST* ps)
{
	assert(ps);
	free(ps->a);
	ps->a = NULL;
	ps->top=ps->capacity = 0;
}
void STPush(ST* ps, Datatype x)
{
	assert(ps);
	if (ps->top == ps->capacity)
	{
		int newcapacity = ps->capacity == 0 ? 4 : ps->capacity * 2;
		Datatype* tmp = (Datatype*)realloc(ps->a, sizeof(Datatype) * newcapacity);
		if (tmp == NULL)
		{
			perror("realloc failed");
			exit(-1);
		}
		ps->a = tmp;
		ps->capacity = newcapacity;
	}
	ps->a[ps->top] = x;
	ps->top++;
}

void STPop(ST* ps)
{
	assert(ps);
	assert(ps->top > 0);
	--ps->top;
}

Datatype STTop(ST* ps)
{
	assert(ps);
	assert(ps->top>0);
	return ps->a[ps->top-1];
}

int STSize(ST* ps)
{
	assert(ps);
	return ps->top;
}

bool STEmpty(ST* ps)
{
	assert(ps);
	return ps->top == 0;
}




